As computers have increased in speed and complexity, so too has the video data transmitted from a processor, motherboard, or graphics card to a video display. Along with this increased complexity comes an increase in the raw amount of video data transmitted. For example, early video displays comprised simple ASCII text, which eventually gave way to monochromatic graphics. This evolution continued through the Color Graphics Adapter (CGA) video standard, the Video Graphics Array (VGA) video format, and so forth to today's high-resolution video display formats. Each step up in video display quality required a concurrent step in the speed with which video data was transmitted, and the development of new video circuitry to meet increasing transmission requirements.
Today, the transition-minimized differential signaling (TMDS) interface is used as a basis for several video display standards, including the VESA Digital Visual Interface (DFP) and “Plug & Display” (P&D) standards, as well as the Digital Visual Interface (DVI) specification from the Digital Display Working Group. The TMDS interface is generally embodied as a microcircuit capable of high speed serial video transmission in a single direction. A TMDS circuit accepts three parallel video data inputs, encodes the video data via a proprietary algorithm, and transmits encoded data as a serial transmission. Further, the TMDS interface is used by many digital video sources, such as digital still cameras, televisions, and video cameras.
However, modern video transmission systems are typically configured as unidirectional transmitters. That is, each system transmits data, but is unable to receive data without the addition of a second specially configured transmission system. For example, the TMDS interface described above requires that each data transmission source have a completely separate TMDS-compatible receiver in order to receive return video data. This adds to the overall design complexity and manufacturing cost when developing video systems based on the TMDS standard. In applications where many simultaneous video transmissions are required, such as a videoconference or multi-camera video shoot, the cost of these extra transmitters and receivers becomes prohibitive.
Accordingly, there is a need for an improved video data transmission system.